In the completion of oil well, a well casing traverses the earth formations and perforations are provided at production levels so that oil or gas from low permeability oil or gas formations may be produced through existing fractures in the formations via the perforations. In many instances, existing vertical fracture may be utilized for production by intercepting these fractures with suitably spaced perforations about the circumference of the well casing. In the drilling of a well, a well control fluid called a "drilling mud" is commonly used to control the well by having a hydraulic pressure greater than the pressure of the fluids in the earth formations. If the pressure of the mud is significantly higher than the pressure in the formations, then fluid from the mud can enter into the earth formations and particles in the mud system tend to block existing vertical features in the formation.
ln a cased well completion, it is necessary to produce the formations through the perforations. With present perforating techniques, it is extremely problematical whether or not a given perforation will intersect a natural vertical fracture. Where the fracture is at an angle to the vertical it is even more difficult to intersect the fracture by the perforation.